Lesson 2: Earth’s Internal Heat Sources

When was Earth formed, and what allows its biotic components to remain alive?

Earth was formed about 4.6 billion years ago, and its biotic components remain alive due to proper regulation of internal heat.

What happens to Earth’s heat as you go deeper from the crust to the inner core?

The heat increases from the crust down to the inner core due to several internal processes.

What are the four main sources of Earth’s internal heat?

(1) Primordial heat, (2) Radioactive decay, (3) Gravitational pressure, (4) Dense core material.

What process formed the earliest stage of Earth that generated primordial heat?

Accretion: gases and dust of clouds were attracted by gravitational energy, forming planetesimals. Their collisions generated heat, making early Earth molten and trapping heat in the core.

How was primordial heat preserved inside Earth?

Through convective transport in the core and mantle, and conductive transport across plate boundaries, which slowed the loss of heat.

What is the main ongoing source of Earth’s internal heat?

Radioactive decay of naturally occurring isotopes.

Define radioactive decay.

Radioactive decay is the spontaneous breakdown of an atomic nucleus, releasing energy and matter.

Name the key isotopes that produce heat in Earth’s interior.

Potassium-40, Uranium-235, Uranium-238, and Thorium-232.

Why does radioactive decay prevent Earth from cooling completely?

Because it continually releases heat energy as a byproduct of nuclear decay.

Gravitational pressure

The more a person descend into Earth’s interior, the amount of pressure

increases due to the force pressing on an area caused by the weight of an overlying

rocks.

The pressure near the center is considered to be 3 to 4 million times the

pressure of atmosphere at sea level

Again, because rocks are good insulators, the

escape of heat from Earth’s surface is less than the heat generated from internal

gravitational attraction or squeezing of rock, so heat builds up within.

At high temperature,

the material beneath will melt towards the central part of the earth.

This molten material under tremendous pressure conditions acquires the property

of a solid and is probably in a plastic state.

Dense core material in the center of the planet

Due to increase in pressure and presence of heavier materials towards the earth’s

center, the density of earth’s layers also increases. Obviously, the materials of the

innermost part of the earth are very dense.

What are the primary elements in Earth’s inner core?

Iron and nickel.

What is the density of Earth’s core, and what does it suggest?

12,600–13,000 kg/m³, suggesting the presence of other heavy elements like gold, platinum, palladium, silver, and tungsten.

How does the descent of dense iron-rich material contribute to Earth’s internal heat?

The sinking of dense iron to the core released heat, producing about 2,000 K of heating.

Why doesn’t the inner core melt despite intense heat?

Because the pressure and density are so great that iron atoms (and other elements) cannot move into a liquid state.

It took a long time for ____ to move from the internal part of the Earth going to its surface.

heat

There had been ______________ of heat within the core to the mantle of the

earth.

convective transport

Earth is considered as ______________ since its main source of internal heat

come from the produced decay of some naturally occurring isotopes from its

interior.

thermal engine

Radioactive decay emits _____________ that prevents the Earth from

completely cooling off.

heat energy

The escape of heat from Earth’s surface is less than the heat generated from internal ______________, so heat builds up within.

gravitational attraction (or pressure)

The ___________ under tremendous pressure conditions acquires the property of a solid and is probably in a plastic state.

molten material

The inner core’s intense pressure prevents the iron and other minimal amount of some elements from ?

melting

The _______ and density are simply too great for the iron atoms to move into a liquid state.

pressure